Relationship among metabolic syndrome, C358A polymorphism of the endocannabinoid degrading enzyme fatty acid amide hydrolase (FAAH) and insulin resistance

Association between the FAAH C385A variant (rs324420) and obesity-related traits: a systematic review

BACKGROUND

Overweight and obesity are the consequence of a sustained positive energy balance. Twin studies show high heritability rates pointing to genetics as one of the principal risk factors. By 2022, genomic studies led to the identification of almost 300 obesity-associated variants that could help to fill the gap of the high heritability rates. The endocannabinoid system is a critical regulator of metabolism for its effects on the central nervous system and peripheral tissues. Fatty acid amide hydrolase (FAAH) is a key enzyme in the inactivation of one of the two endocannabinoids, anandamide, and of its congeners. The rs324420 variant within the FAAH gene is a nucleotide missense change at position 385 from cytosine to adenine, resulting in a non-synonymous amino acid substitution from proline to threonine in the FAAH enzyme. This change increases sensitivity to proteolytic degradation, leading to reduced FAAH levels and increased levels of anandamide, associated with obesity-related traits. However, association studies of this variant with metabolic parameters have found conflicting results. This work aims to perform a systematic review of the existing literature on the association of the rs324420 variant in the FAAH gene with obesity and its related traits.

METHODS

A literature search was conducted in PubMed, Web of Science, and Scopus. A total of 645 eligible studies were identified for the review.

RESULTS/CONCLUSIONS

After the identification, duplicate elimination, title and abstract screening, and full-text evaluation, 28 studies were included, involving 28 183 individuals. We show some evidence of associations between the presence of the variant allele and higher body mass index, waist circumference, fat mass, and waist-to-hip ratio levels and alterations in glucose and lipid homeostasis. However, this evidence should be taken with caution, as many included studies did not report a significant difference between genotypes. These discordant results could be explained mainly by the pleiotropy of the endocannabinoid system, the increase of other anandamide-like mediators metabolized by FAAH, and the influence of gene-environment interactions. More research is necessary to study the endocannabinoidomic profiles and their association with metabolic diseases.

Fatty Acid Amide Hydrolase: An Integrative Clinical Perspective

Introduction: Fatty acid amide hydrolase (FAAH) is one of the main terminating enzymes of the endocannabinoid system (ECS). Since being discovered in 1996, the modulation of FAAH has been viewed as a compelling alternative strategy to obtain the beneficial effect of the ECS. With a considerable amount of FAAH-related publication over time, the next step would be to comprehend the proximity of this evidence for clinical application. Objective: This review intends to highlight the rationale of FAAH modulation and provide the latest evidence from clinical studies. Methods: Publication searches were conducted to gather information focused on FAAH-related clinical evidence with an extension to the experimental research to understand the biological plausibility. The subtopics were selected to be multidisciplinary to offer more perspective on the current state of the arts. Discussion: Experimental and clinical studies have demonstrated that FAAH was highly expressed not only in the central nervous system but also in the peripheral tissues. As the key regulator of endocannabinoid signaling, it would appear that FAAH plays a role in the modulation of mood and emotional response, reward system, pain perception, energy metabolism and appetite regulation, inflammation, and other biological processes. Genetic variants may be associated with some conditions such as substance/alcohol use disorders, obesity, and eating disorder. The advancement of functional neuroimaging has enabled the evaluation of the neurochemistry of FAAH in brain tissues and this can be incorporated into clinical trials. Intriguingly, the application of FAAH inhibitors in clinical trials seems to provide less striking results in comparison with the animal models, although some potential still can be seen. Conclusion: Modulation of FAAH has an immense potential to be a new therapeutic candidate for several disorders. Further exploration, however, is still needed to ensure who is the best candidate for the treatment strategy.

Potential of Fatty Acid Amide Hydrolase (FAAH), Monoacylglycerol Lipase (MAGL), and Diacylglycerol Lipase (DAGL) Enzymes as Targets for Obesity Treatment: A Narrative Review

The endocannabinoid system (ECS) plays an integral role in maintaining metabolic homeostasis and may affect hunger, caloric intake, and nutrient absorption. Obesity has been associated with higher levels of the endogenous cannabinoid transmitters (endocannabinoids). Therefore, the ECS is an important target in obesity treatment. Modulating the enzymes that synthesize and degrade endocannabinoids, namely fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and diacylglycerol lipase (DAGL), may be a promising strategy to treat obesity. This review aims to synthesize all studies investigating pharmacological or genetic manipulation of FAAH, MAGL, or DAGL enzymes in association with obesity-related measures. Pharmacological inhibition or genetic deletion of FAAH tended to promote an obesogenic state in animal models, though the relationships between human FAAH polymorphisms and obesity-related outcomes were heterogeneous, which could be due to FAAH having both pro-appetitive and anti-appetitive substrates. Genetic deletion of Mgll and Dagla as well as pharmacological inhibition of DAGL tended to reduce body weight and improve metabolic state in animal studies, though the effects of Mgll manipulation were tissue-dependent. Monitoring changes in body weight in ongoing clinical trials of FAAH inhibitors may clarify whether FAAH inhibition is a potential therapeutic strategy for treatment obesity. More preclinical work is needed to characterize the role of MAGL and DAGL modulation in obesity-related outcomes.

Genetic polymorphisms of the endocannabinoid system in obesity and diabetes

The endocannabinoid system (ECS) is involved in many physiological processes including fertility, pain and energy regulation. The aim of this systematic review was to examine the contribution of single nucleotide polymorphisms (SNPs) of the ECS to adiposity and glucose metabolism. Database searches identified 734 articles, of which 65 were included; these covered 70 SNPs in genes coding for cannabinoid receptors 1 and 2 (CB₁ , CB₂ ), fatty acid amide hydrolase (FAAH) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). No studies included SNPs relating to monoacylglycerol lipase or diacylglycerol lipase. The CB₁ receptor SNP rs1049353 showed 17 associations with lower body mass index (BMI) and fat mass (five studies). It also showed three associations with lower insulin levels (one study). Conversely, the CB₁ receptor SNP rs806368 was associated with increased BMI and waist circumference (two studies). The FAAH SNP rs324420 was associated with increased obesity (three studies). A haplotype of NAPE-PLD was associated with decreased BMI (one study). A total of 60 SNPs showed no association with any measured outcome. This review suggests a complex but important role of ECS SNPs in energy and glucose metabolism.

Association of polymorphisms in the endocannabinoid system genes with myocardial infarction and plasma cholesterol levels

AIMS

The aim of this study was to investigate the relationship between selected symptoms of chronic heart failure (myocardial infarction, plasma cholesterol level) and single nucleotide polymorphisms (SNPs) in the FAAH and CNR1 genes.

METHODS

A case - control study involving 155 patients with chronic heart failure and 169 age- and sex-matched healthy subjects. We detected SNPs 385 C/A (rs324420) in the FAAH and 1359 G/A (rs1049353) in the CNR1 genes using the polymerase chain reaction and restriction analysis. Genotype and allele frequencies were compared between patients and controls as well as between patients with and without myocardial infarction.

RESULTS

No significant differences in genotype or allelic frequencies between patients and controls were found (P > 0.05). Carriers of the FAAH A allele had a 2.37-fold increase in the risk of myocardial infarction (odds ratio 2.37, 95% confidence interval 1.36-6.93, P = 0.01). Homozygous carriers of genotype AA of CNR1 SNP 1359 had significantly higher plasma cholesterol levels than carriers of GG and GA genotypes in patients (P = 0.04).

CONCLUSIONS

The study results suggest a role for allele A of the FAAH 385 variant as a risk factor for myocardial infarction. Genotype AA of CNR1 1359 variant probably affects plasma cholesterol levels. Pharmacological intervention in this system could modify the therapeutic approach to certain cardiovascular disorders.

Genetic variation in the endocannabinoid degrading enzyme fatty acid amide hydrolase (FAAH) and their influence on weight loss and insulin resistance under a high monounsaturated fat hypocaloric diet

BACKGROUND AND AIMS

The C385A polymorphism of FAAH gene (rs324420C>A) has been associated with obesity. We investigate the role of this polymorphism on anthropometric and metabolic responses after an enriched monounsaturated fat hypocaloric diet.

METHODS

A sample of 95 obese individuals was analyzed at baseline and after 3 months of an enriched monounsaturated fat hypocaloric diet.

RESULTS

Sixty two patients (65.3%) had the genotype C385C and 33 (34.7%) patients had C385A genotype (30 patients, 31.6%) or A358A (3 patients, 3.2%) (A carriers group). In subjects with C385C genotype, insulin (-1.9±5.3 mUI/l) and HOMA-R (-0.48±0.75 U) decreased. In A carriers subjects, the decreases in weight were 3.7±3.4 kg (decrease in C385C genotype group 4.4±3.6 kg), fat mass 2.7±3.2 kg (decrease in C385C genotype group 3.4±3.2 kg) and waist circumference 3.1±3.4cm (decrease in C385 genotype group 4.4±4.6 cm). These changes were significantly higher in the C385C genotype group than the A carriers subjects.

CONCLUSION

After weight loss, noncarriers of the allele A385 of FAAH had an improvement on insulin and HOMA-R levels with an enriched monounsaturated fat hypocaloric diet. A better response of weight, fat mass and waist circumference was observed in C385 genotype subjects than A carriers participants.